1. Field of the Invention
This invention relates to an occupant powered scooter and, more particularly, to a pedal drive system for a scooter.
2. Description of Related Art
Skateboards and scooters have become ubiquitous in many parts of the world, due to the plethora of new designs and features that have been introduced in recent years. Accompanying the introduction of high performance bearings and wheels at affordable prices, an entirely new recreational field has been created for children and adults.
Skateboards and scooters share some common features, including a platform on which the rider is supported, and front and rear wheels for supporting the platform for rolling on a smooth surface. A scooter is generally distinguished from a skateboard by the provision of steerable front wheels that are controlled by a tiller or handlebar, whereas a skateboard is steered by shifting weight and thrust of the rider. In both forms of transport, it is common for the rider to propel the vehicle by supporting the rider's weight with one foot on the platform, and reaching the other foot to the ground and pushing rearwardly to create forward motion. However, as ground speed increases, the propelling foot must push against a ground surface that is receding rearwardly at a rapid rate. Thus the force of propulsion by foot diminishes as the vehicle speed increases, and it becomes increasingly difficult to exceed a rather low maximum velocity on a flat surface. (Downhill speed is limited by other factors, such as air resistance, wheel resistance, and the like.)
This inherent limitation in direct foot propulsion has been addressed in the prior art. U.S. Pat. Nos. 6,079,727; 6,131,933; 6,241,269; and 6,270,102 all issued to the present inventor, describe mechanisms for propulsion of skateboards and scooters of various configurations. The present invention represents further improvements over these prior art devices.
One problem common to these vehicles is that the propulsion mechanism may extend below the platform that supports the rider. The platform must be close to the ground to avoid instability, and the depending mechanism reduces ground clearance and increases the probability of collision with small obstacles such as curbs, bumps, holes, or uneven pavement. On the other hand, placing the mechanism on top of the platform concomitantly reduces the area on which the rider may stand. Furthermore, the mechanism must be protected from the rider's feet, and vice versa. Another problem common to these vehicles is that the driving mechanism is mounted on one side of the longitudinal axis of the platform, thus causing instability of the vehicle due to uneven weight distribution of the driving components.